The present invention is related to a composite heat-dissipating system and its used fan guard, and more particularly to a fan guard, adapted to be used with a heat-dissipating device, which imparts a supercharging function to the heat-dissipating device for efficient heat dissipation and reduces the noise generated when the heat-dissipating device is operated.
Currently, heat-dissipating fans commonly used in personal computers include an axial-flow fan, a centrifugal fan and a cross-flow fan. Of these, the most popular one is supposed to be an axial-flow fan.
Referring to FIG. 1, a conventional axial-flow fan is primarily consisted of a rotor device 10 and a frame 11 arranged beside the rotor device for supporting the rotor device. The frame 11 includes a motor holder (not shown) and a plurality of ribs 13 arranged between the outer frame 11 and the motor holder. The rotor device 10 includes a motor (not shown) received on the motor holder and a plurality of rotor blades 12 to work on the surrounding air to generate an airflow. Through the work of the rotor blades on the surrounding air, the blast pressure is changed from a relatively low value on the air inlet side into a relatively high value on the air outlet side. That is, there is a blast pressure enhancement on the air outlet side.
Unfortunately, when the airflow flows through the fan having the structure as shown in FIG. 1 and as described above, turbulent flows will be generated after the airflow encounters the ribs so as to have an adverse effect on the blast pressure enhancement. Consequently, the efficiency of the fan is reduced.
In addition, in order to avoid the interruption of operation due to the breakdown of fan used in the heat-generating system, a set of standby fan is usually provided and connected with the original fan in series to prevent the heat-generating system or device from being damaged. Moreover, because the total pressure of the axial-flow fan is relatively low, the axial-flow fan cannot fully develop a high airflow rate in a system of a high resistance. Thus, in the case that a high total pressure is needed, two or more axial-flow fans are connected in series to provide the high total pressure.
Typically, a so-called serial fan is constituted by two independent fan units assembled through a specific circuit design. Each fan unit respectively includes a frame and a rotor device. After these two fan units are assembled respectively, both of them are coupled together through screws (not shown), thereby completing the construction of the serial fan. However, the serial connection of two fan units can not guarantee that the total pressure of the airflow discharged from the fans can be doubled. In other words, even though one fan unit rotates and the other is used as a standby fan, the latter will also decrease the blast pressure discharged from the rotating fan because both of them will be interfered with each other while connected in series, thereby significantly decreasing the overall heat-dissipating efficiency or even generating a lot of noise.
Therefore, it is desirable to develop a heat-dissipating system which can effectively eliminate the interference between the fans assembled together, provide a supercharging function, and reduce the noise generated when the fans are operated.
Therefore, an object of the present invention is to provide an improved fan guard having a function of supercharging a heat-dissipating fan.
Therefore, another object of the present invention is to provide a composite heat-dissipating system which can effectively eliminate the interference between the heat-dissipating fans assembled together.
Therefore, another yet object of the present invention is to provide a composite heat-dissipating system which can provide a supercharging function and reduce the noise generated when the fans assembled together are operated.
The fan guard essentially includes a frame, and a plurality of guard blades radially arranged inside the frame and fixed onto an inner surface of the frame by each one end thereof. In general, the guard blades are made of plastic. Nevertheless, the guard blades can also be made of a material other than plastic for a desired purpose. For example, they can be made of a metal which is advantageous for heat dissipation.
When assembled with the heat-dissipating device, the frame of the fan guard is coupled to the main frame of the heat-dissipating device. Alternatively, the frame of the fan guard is integrally formed with the frame of the heat-dissipating device so that the fan can be assembled by installing the non-integrally formed parts into the common frame. The fan guard can be arranged either upstream or downstream of the heat-dissipating device. Preferably, the fan guard includes two sets of frame and guard blades respectively arranged by both sides of the heat-dissipating device. By properly designing the shapes and the position arrangement of the guard blades relative to the rotor blades of the heat-dissipating device, the upstream guard blades can guide air into the heat-dissipating device at an angle to make an air inflow to the heat-dissipating device have an additional tangential velocity which increase the work of the rotor blades on air, and on the other hand, the downstream guard blades can transform a tangential velocity of an air outflow from the heat-dissipating device into a static pressure, both advantageous for supercharging the fan. For example, each of the guard blades is made to have a shape identical to those of the rotor blades, but not limited to such a shape. For example, the cross-sectional shape of each guard blade can be plate, triangle, trapezoid or wing, prefereably a cross-sectional shape with a linear central line and one of a curve and an arc. Alternatively, each guard blade has a curved face, an arcuate face, a curve or an arc.
Furthermore, by taking the combination of a fan guard according to the present invention and a heat-dissipating device as a fan unit, a fan can be designed to include a plurality of such fan units to enhance heat-dissipating efficiency. In addition, this constructed fan unit can also be assembled with another fan unit in series or in parallel.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: